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Summary: Methods | Inherited Methods

# WritableIdentityCredential

`public abstract class WritableIdentityCredential`
`extends Object` ``

java.lang.Object
↳ | android.security.identity.WritableIdentityCredential

Class used to personalize a new identity credential.

Credentials cannot be updated or modified after creation; any changes require deletion and re-creation. Use `IdentityCredentialStore#createCredential(String, String)` to create a new credential.

## Summary

### Public methods
`abstract Collection<X509Certificate>` | `getCredentialKeyCertificateChain(byte[] challenge)` Generates and returns an X.509 certificate chain for the CredentialKey which identifies this credential to the issuing authority.
`abstract byte[]` | `personalize(PersonalizationData personalizationData)` Stores all of the data in the credential, with the specified access control profiles.

### Inherited methods
From class `java.lang.Object`
`Object` | `clone()` Creates and returns a copy of this object.
`boolean` | `equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void` | `finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>` | `getClass()` Returns the runtime class of this `Object`.
`int` | `hashCode()` Returns a hash code value for the object.
`final void` | `notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void` | `notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String` | `toString()` Returns a string representation of the object.
`final void` | `wait(long timeout, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void` | `wait(long timeout)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void` | `wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

## Public methods

### getCredentialKeyCertificateChain

    public abstract Collection<X509Certificate> getCredentialKeyCertificateChain (byte[] challenge)

Generates and returns an X.509 certificate chain for the CredentialKey which identifies this credential to the issuing authority. The certificate contains an Android Keystore attestation extension which describes the key and the security hardware in which it lives.

Additionally, the attestation extension will contain the tag Tag::IDENTITY_CREDENTIAL_KEY which indicates it is an Identity Credential key (which can only sign/MAC very specific messages) and not an Android Keystore key (which can be used to sign/MAC anything).

The issuer MUST carefully examine this certificate chain including (but not limited to) checking that the root certificate is well-known, the tag Tag::IDENTITY_CREDENTIAL_KEY present, the passed in challenge is present, the tag Tag::ATTESTATION_APPLICATION_ID is set to the expected Android application, the device has verified boot enabled, each certificate in the chain is signed by its successor, none of the certificates have been revoked, and so on.

It is not strictly necessary to use this method to provision a credential if the issuing authority doesn't care about the nature of the security hardware. If called, however, this method must be called before `personalize(android.security.identity.PersonalizationData)`.

Parameters
`challenge` | `byte`: is a non-empty byte array whose contents should be unique, fresh and provided by the issuing authority. The value provided is embedded in the attestation extension and enables the issuing authority to verify that the attestation certificate is fresh. This value cannot be `null`.

Returns
`Collection<X509Certificate>` | the X.509 certificate for this credential's CredentialKey. This value cannot be `null`.

### personalize

    public abstract byte[] personalize (PersonalizationData personalizationData)

Stores all of the data in the credential, with the specified access control profiles.

This method returns a COSE_Sign1 data structure signed by the CredentialKey with payload set to `ProofOfProvisioning` as defined below.

         ProofOfProvisioning = [
              "ProofOfProvisioning",        ; tstr
              tstr,                         ; DocType
              [ * AccessControlProfile ],
              ProvisionedData,
              bool                          ; true if this is a test credential, should
                                            ; always be false.
          ]

          AccessControlProfile = {
              "id": uint,
              ? "readerCertificate" : bstr,
              ? (
                   "userAuthenticationRequired" : bool,
                   "timeoutMillis" : uint,
              )
          }

          ProvisionedData = {
              * Namespace => [ + Entry ]
          },

          Namespace = tstr

          Entry = {
              "name" : tstr,
              "value" : any,
              "accessControlProfiles" : [ * uint ],
          }

This data structure provides a guarantee to the issuer about the data which may be returned in the CBOR returned by `ResultData#getAuthenticatedData()` during a credential presentation.

Parameters
`personalizationData` | `PersonalizationData`: The data to provision, including access control profiles and data elements and their values, grouped into namespaces. This value cannot be `null`.

Returns
`byte[]` | A COSE_Sign1 data structure, see above. This value cannot be `null`.

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